1. Field of the Invention
The present invention relates to a semiconductor module, particularly to a heat sink for a semiconductor module used as an extended or expanded memory module in a personal computer or the like. Also, the present invention relates to a semiconductor module in which the above-mentioned heat sink for a semiconductor module is incorporated.
2. Description of the Related Art
First, the structure of a semiconductor module, especially that generally used as an extended or expanded memory module in a personal computer or the like, will be described with reference to FIG. 14.
A memory module 10 is comprised of a circuit board 12 having a plurality of terminals 11 formed along an edge thereof, and a plurality of semiconductor memories 14 mounted on both surfaces of the circuit board 12. The semiconductor memory 14 may be mounted in various ways. For example, a memory element (memory chip) itself which is a semiconductor element is directly carried on the circuit board by a flip-chip method or others, or the memory element may be packaged with resinous material together with a lead frame to form a semiconductor device which is then mounted onto the circuit board. Alternatively, the semiconductor memory may be of a chip-size package type such as xcexc BGA.
Next, a structure of a prior art heat sink used in this memory module 10 as well as an attachment structure therefor will be described with reference to FIGS. 14 to 16.
A heat sink 16 is constructed by a pair of metallic plates 18, each formed to have a generally rectangular contour similar to that of the circuit board 12 and have a size sufficient for covering an overall area in the circuit board 12 mounting the semiconductor memories 14 thereon. A recess 20 is formed in the respective metallic plate 18, having dimensions capable of receiving the semiconductor memory 14 of a certain thickness attached to the surface of the circuit board 12 so that an inner surface of the metallic plate 18 is brought into close contact with a back surface of the semiconductor memory 14 when the metallic plates 18 is brought into close contact with the both sides of the circuit board 12, respectively.
The heat sink 16 is attached to the circuit board 12 while using a plurality of through-holes 24 provided at positions corresponding to a plurality of (e.g. four) attachment holes 22 provided in the circuit board 12.
The heat sinks 16 are arranged on the respective sides of the memory module 10 so that all of the through-holes 24 provided in the respective heat sink are aligned with the respective attachment holes corresponding thereto.
Then, a rivet 26 is inserted into the through-hole 24 of the heat sink 16 and the attachment hole 22 thus aligned to each other, while protecting opposite ends of the rivet 26 out of the holes 22, 24. The projected ends are hammered to have a larger diameter. Thereby, the heat sinks 16 are attached to the both surfaces of the memory module 10.
However, there is a problem when the heat sinks 16 are attached to the memory module 10 in the above-mentioned manner, in that the operation is extremely troublesome, for bringing the heat sinks 16 into close contact with the circuit board 12 of the memory module 10 via a tape 28 while positioning the through-holes 24 to the attachment holes 22 corresponding thereto and inserting the rivets 26 one by one into the respective through-holes 24 aligned with the attachment holes 22, after which the projected ends of the rivet are hammered to secure the heat sink 16 to the memory module 10.
This is because there is no positioning mechanism between the circuit board 12 and the heat sink 16, whereby the alignment between both the holes is liable to be disturbed, by a trifling cause, to prevent the rivets 26 from being inserted.
Accordingly, the present invention has been made to solve the above-mentioned problem in the prior art, and an object thereof is to provide a heat sink for a semiconductor module capable of being easily attached to the semiconductor module.
Another object of the present invention is to provide a semiconductor module on which the heat sink for a semiconductor module is mounted.
According to the present invention, there is provided a heat sink adapted to be used for a semiconductor module, the heat sink comprising: a pair of metallic plates, between which a circuit board having attachment holes is to be disposed, in such a manner that spaces are defined between the circuit board and the pair of metallic plates for accommodating semiconductor elements or semiconductor devices mounted on the circuit board, when the pair of metallic plates are attached to the circuit board; one of the metallic plates provided at positions corresponding to the attachment holes with through holes; the other metallic plate provided at positions corresponding to the attachment holes with tubular projections having a length larger than a sum of a thickness of the circuit board and a thickness of the one metallic plate; and the tubular projections capable of being inserted into the attachment holes and the through holes, and tip ends of the tubular projections capable of being enlarged so as to firmly attach the pair of metallic plates to the circuit board.
The tubular projections are integrally formed with the other metallic plate.
The pair of metallic plates are integrally connected to each other by means of a connecting portion having a width substantially the same as the thickness of the circuit board, so that the pair of metallic plates can be bent along the connecting portion so as to be attached to the circuit board.
Thin portions are provided at boundaries between the connecting portion and the metallic plates, so that the pair of metallic plates can easily be bent along the thin portions to be attached to the circuit board.
According to another aspect of the present invention, there is provided a heat sink adapted to be used for a semiconductor module, the heat sink comprising: a pair of same or symmetrical metallic plates, between which a circuit board having at least a pair of attachment holes is to be disposed, in such a manner that spaces are defined between the circuit board and the pair of metallic plates for accommodating semiconductor elements or semiconductor devices mounted on the circuit board, when the pair of metallic plates are attached to the circuit board; each of the metallic plates provided at a position corresponding to one of the attachment holes with a through holes and at a position corresponding to the other attachment hole with a tubular projection having a length larger than a sum of a thickness of the circuit board and a thickness of the metallic plate; and the tubular projections of the respective metallic plates capable of being inserted into the attachment holes and the through holes of the respective other metallic plates and tip ends of the tubular projections capable of being enlarged so as to firmly attached the pair of metallic plates to the circuit board.
According to still another aspect of the present invention, there is provided a heat sink adapted to be used for a semiconductor module, the heat sink comprising: a pair of metallic plates, between which a circuit board, having attachment holes, is to be disposed in such a manner that spaces are defined between the circuit board and the pair of metallic plates for accommodating semiconductor elements or semiconductor devices mounted on the circuit board, when the pair of metallic plates are attached to the circuit board; each of the metallic plates provided at positions corresponding to the attachment holes with through holes; the pair of metallic plates integrally connected to each other by means of a connecting portion having a width substantially same as the thickness of the circuit board; and thin portions provided at a boundary between the connecting portion and the metallic plates, so that the pair of metallic plates can easily be bent along the thin portions to be attached to the circuit board.
According to another aspect of the present invention, there is provided a semiconductor module comprising: a circuit board provided with a plurality of attachment holes; semiconductor elements or semiconductor devices mounted on the circuit board; a pair of metallic plates, as mentioned above.
The tip ends of the tubular projections are enlarged by hammering.